ZrO_2陶瓷激光冲击预处理研究

Micro-Plastic Deformation of ZrO_2 in High Strain Rate by Laser Shocking

为研究超二氧化锆(ZrO2)陶瓷的冲击增韧特性,利用能量为35 J的激光脉冲对ZrO2陶瓷试样进行冲击试验,并对试样进行扫描电镜(SEM)检测。结果表明试样表面产生了约90μm厚的无裂纹的致密层,后表面出现了层裂破坏,在非致密层内则产生大量微观裂纹,微裂纹密度越靠近试样后表面越大。X射线物相分析结果表明部分材料发生了从四方相到单斜相的冲击相变,而这一相变过程会导致组织体积增加。发生在裂纹尖端的冲击相变因体积增加产生残余压应力,阻碍裂纹的扩展,使裂纹具有非扩展性。大量非扩展性微裂纹的存在可提高ZrO2陶瓷的冲击韧性,利用10 J能量的激光脉冲对试样进行多点冲击预处理,然后利用42 J的激光脉冲对试样进行冲击,结果表明预处理后的试样后表面仅出现层裂倾向,而没有发生层裂破坏。说明激光冲击预处理达到了增加冲击韧性的目的。

The ZrO2 ceramic sample has been shocked by laser pulse with 35 J energy and determined with scanning electron microscope （SEM） for researching on the impact toughness. The results show that a compact layer with 90 μm thickness that there is no cracks in is formed in the laser irradiated surface of the sample,and a lot of micro-cracks which its density increased as nearing to the back were observed under the compact layer,while the spallation occurred in the back of the sample. The X-ray phase analysis for ZrO2 ceramic indicate that the impact phase transition from tetragonal phase to monoclinic phase has occurred in some materials,which may lead to the volume of metallographic structure increasing. The residual stress produce by the transition in the tip of cracks will hinder cracks expanding,so the cracks have no expandability. A ceramic sample has been shocked by laser pulse with 10 J energy repeatedly,and then shocked by laser pulse with 42 J energy,the pretreatment results show that the spallation tendency appears in the sample back,but no spallation occurred in there,so it suggests that the laser shocking pretreatment can increase the impact toughness.